This invention relates to a gas spring of the type in which a piston assembly reciprocates in an elongated cylinder closed at one end and open at the other with a rod connected to the piston assembly and projecting through the open end of the cylinder. The cylinder is sealed at its open end by a sealing assembly which seals the space between the rod and the inner wall of the cylinder while permitting the rod to reciprocate with the piston assembly. Inside the cylinder is a body of oil and a gas under pressure. The invention has more particular reference to a gas spring wherein the sealing assembly also serves as a reservoir of oil for the cylinder. An example of such a gas spring is shown in Skubal U.S. Pat. No. 4,108,423.